JP5004962B2 - Method and apparatus for producing a predetermined pattern on a silicon panel - Google Patents

Description

The present invention relates to a method for manufacturing a silicon panel according to the preamble of claim 1.

Such a method is widely known. An example of such a method is the foil drawing method known as Ribbon Growth on Substrate (RGS). In this method, the casting frame is filled with, for example, liquid silicon. Also, stay the casting frame is in place, where the band-shaped substrate passes under the casting frame, the band-shaped substrate surface is driven into contact with the silicon melt is used Yes. The crystallized silicon foil escapes at this point to the casting frame side where the band-shaped substrate leaves the casting frame. The silicon foil is divided into a plurality of pieces, and these pieces can serve as a base member for manufacturing a solar cell, for example.

  It is known that the surface of a solar cell has a predetermined structure in order to reduce reflection of incident light on the surface. As an example for this purpose, a plurality of grooves are provided to increase the surface of the solar cell, thereby improving the efficiency of the solar cell.

  Patent publication US 5704992 describes a method of forming a V-shaped groove in a foil with special saw teeth. The saw blade has a sharp outline and rotates at high speed. Also, according to publication US Pat. No. 4,608,451, a predetermined structure is introduced on the surface of the metal foil. In the latter publication, a plurality of grooves are etched into the foil. A predetermined mask is attached to the foil, on which the mask is brought into contact with the etching material. In this case, V-shaped grooves can also be formed in the foil. It is also possible to apply a bumpy or two-dimensional structure by etching to obtain the same effect.

  However, when these techniques are used, the metal foil needs to be further processed after manufacture in order to obtain the desired structure on the surface.

The publication JP2001206798 describes an apparatus that can produce a silicon panel formed by a foil drawing method. A rotating substrate is used on which silicon crystallization occurs. The surface of the substrate is not machined, so the manufactured silicon panel is provided with a sawtooth structure on the surface, for example. This increases the effective area and improves the efficiency of the solar cell.

The foil drawing method is ideal for producing very thin foils. Such a foil can be manufactured to have a thickness of less than 250 μm. The main advantage of this method is that the amount of silicon per panel, for example a solar cell, is very limited. The disadvantage of a very thin silicon panel is that the silicon panel can be easily broken. Such a risk is especially true in the further production of solar cells.

It is an object of the present invention to produce a thin silicon panel by a foil drawing method that produces a panel that is stronger than a panel produced by the prior art. The purpose is that the substrate has at least one second groove having a dimension such that it is substantially filled with liquid silicon , and the at least one second groove is formed in the silicon panel. This is achieved by a method as shown in the introduction part, characterized in that a reinforcement part is formed on the introduction part.

The reinforcing portion is formed in the silicon panel by forming one or more second grooves on the substrate. These reinforcing portions reinforce the panel as a whole, and the rest of the panel can remain thin.

In one implementation liquid, the silicon panel has an average thickness of 100 to 350 μm over the entire surface excluding the reinforcing portion.

  Preferably, the at least one second groove has a depth of 50 to 500 μm.

  In one embodiment, the at least one second groove has a width of 2 to 5 mm.

In a further embodiment, the at least one second groove has a bottom surface extending substantially parallel to the top surface of the silicon panel.

In a further embodiment, the substrate has at least one of a recess and a protruding portion on one surface of the substrate so that the same pattern is formed on the surface of the silicon panel. The recess may have a depth, a width and an inclination angle of the side wall so that the silicon melt is filled. The recess may have a depth and width such that a bridge is formed by crystallized silicon .

In a specific embodiment, the cross section of the plurality of first grooves is large enough to be filled with the silicon melt , and the plurality of second grooves are large enough not to be filled with the silicon melt . The plurality of first grooves may be deep enough to form a protruding portion in the foil that functions as a silicon contact after processing by a roller printing method, for example.

The recess is preferably narrower than 1 mm. Such narrow grooves in the substrate are bridged during crystallization by silicon . Using this method, very thin foils can be produced with V-shaped parallel grooves on one side that can increase the effective area of the solar cell, for example. Such a large surface improves the optical properties and increases the efficiency of the solar cell.

In an embodiment of the present invention, the recess has a plurality of cavities, and the cavities have dimensions such that holes are respectively formed in the foil at points formed in the substrate. The holes thus formed can be used, for example, in the next step in which the silicon contacts at the front and back of the foil are connected to each other. It is no longer necessary to specially form these holes, for example using a laser. These holes preferably have a width of 1 mm to 2 mm.

  In another embodiment, the protruding portion has a band. These bands are protruding portions provided on a substrate having a predetermined length. These protruding portions may be straight or curved. In particular embodiments, the cross-sections of these bands are considered zigzag shaped. Such a special zigzag shape can be used, so to speak, to form a zigzag structure in the foil. Thereby, the efficiency of a solar cell can be improved.

This invention also provides a silicon panels manufactured by the method described above, related to the apparatus for manufacturing a silicon panel.
Further advantages and features of the invention are explained in detail in connection with the description of the individual embodiments with reference to the attached drawings.

FIG. 1 shows a schematic side view of a foil drawing device according to an embodiment of the present invention. The apparatus for producing this silicon foil consists of a casting frame 2 into which liquid silicon , i.e. a silicon melt, can be poured. Silicon melt (metal melt) 4, also referred Silicone fluid 4, the supply device 6, is injected into the casting frame 2. The casting on the lower side of the frame 2, in the form of base band 8 which is designed to move under the casting frame 2 at a predetermined speed while in contact with the silicon melt by ejecting silicon melt, i.e. There is a band-shaped substrate 8. The drive means required for this is shown in FIG. The foil pulling device also has a control module 10 and a height measuring device 12 designed to determine the height of the liquid silicon 4 in the casting frame 2. Temperature of the band-shaped substrate 8, liquid silicon 4 so that crystallization at the surface of the band-shaped substrate 8, is adjusted. A typical temperature of liquid silicon is 1200 ° C. Since the band-shaped substrate 8 moves to the right in FIG. 1, the foil 16 escapes to the downstream side of the casting frame 2. The foil 16 pushes the casting frame 2 upward on the downstream side to slightly tilt the casting frame. The band-shaped substrate 8 is provided with a plurality of groove portions 17 orthogonal to the moving direction at regular intervals. The grooves 17 have such widths and depths that the liquid silicon 4 does not flow into the grooves 17 due to the surface tension of the liquid silicon , but the interruptions 18 are formed in the silicon foil 16. ing. For this reason, a rectangular foil suitable for solar cells can be produced very simply. These rectangular foils cool and eventually shrink slightly. Accordingly, these foils are separated from the band-shaped substrate 8. These foils can then be removed from the band-shaped substrate 8 by means of a robot arm, for example for further processing.

FIG. 2 shows a top view of a band-shaped substrate 8 according to one embodiment of the present invention. The substrate 8 has a groove 21 having a width of 3 mm, for example. The groove 21 is sized to be filled with liquid silicon. The band-shaped substrate 8 has a pattern of recesses 22, 23, 24, and 25 in the longitudinal direction of the band-shaped substrate 8. Relatively wide grooves 32 and 34 are provided in the longitudinal direction on both sides of the band-shaped substrate 8. These groove parts 32 and 34 and the groove part 17 are disclosed in particular in EP 0497148 and determine the dimension of the foil 16 (piece). The shape and depth of the grooves 32 and 34 prevent the liquid silicon 4 from reaching the grooves 32 and 34 due to surface tension. Accordingly, the liquid silicon 4 cannot reach the other side (outside) of the groove portions 32 and 34. This is because the casting frame 2 has a dimension such that the liquid silicon 4 contacts the band-shaped substrate 8 only inside the groove portions 32 and 34 (or just above the edges of the groove portions). It is.

FIG. 3 shows a cross-sectional view of the band-shaped substrate 8 of FIG. In this example, the recesses 22, 23, 24, 25 are V-shaped grooves. The widths of the grooves 22, 23, 24, and 25 and the inclination angles of the side walls are set so that liquid silicon does not crystallize in these grooves. Instead, the liquid silicon forms a bridge across these grooves. This is shown in FIG. 4 and the foil is indicated by 16. However, the groove 21 is filled with silicon. After crystallization, a thick part of the silicon panel is formed at this location. This thick part reinforces the silicon panel as a whole. Thus, this thick part can be accurately referred to as a reinforcing part. In FIG. 2, the groove 21 extends parallel to one edge of the band-shaped substrate 8. The direction of the groove portion 21 and the recesses 22, 23, 24, and 25 may be different. For example, a predetermined angle may be formed with respect to the edge of the band-shaped substrate 8. Further, the groove portion 21 can have a length different from the length of the recesses 22, 23, 24, 25.

  2 to 4 simply show four narrow grooves for the sake of simplicity. This number is very large, for example over 1000. A typical value of the width of the grooves 22 to 25 in this embodiment is 0.1 to 1 mm. Also, the sidewall inclination angle α (see FIG. 3) is typically less than 20 °. In these figures, the relative width of the groove 21 is not accurately reproduced. A typical value for this groove is 2 to 5 mm.

In another embodiment, the substrate 8 comprises a plurality of recesses having a depth, width and sidewall inclination angle α such that it is filled with liquid silicon . If the side wall tilt angle α is relatively large with respect to the dimensions of these recesses, the liquid silicon is filled into the recesses. In such a case, the groove portion is not formed in the foil 16, but instead, a protruding portion such as a bar or a strip is formed. It is also possible for the recess to be provided, for example, with a small, round cavity completely locally in the substrate 8, thus giving the foil 16 a knob part. Such knob portions can be used for marking for conveyor systems.

FIG. 5 shows an embodiment in which the substrate 8 has two grooves 52 and 54. The inclination angles of the grooves 52 and 54 are about 0 °. However, the grooves 52 and 54 are wide enough to fill the grooves 52 and 54 with liquid silicon . The typical width of these grooves 52 and 54 is 2 to 5 mm. Moreover, the typical depth of these groove parts 53 and 54 is 0.2 to 2 mm. It should be noted that the tilt angle α can have a value greater than, for example, 0 to 45 °. FIG. 6 shows two solar cells 60 and 61 formed of a substrate as shown in FIG. The reinforcing portions 64 and 65 of the solar cell 60 and the reinforcing portions 66 and 67 of the solar cell 61 are used to reinforce the positioning of the metal connection portion on top of these solar cells (“bus bars”). ing. The reinforcing portion 64 is connected to the front surface of the solar cell by a metal joint 70 where the solar cell has the reinforcing portion 66. The reinforcing portion 65 is connected to the front surface at the reinforcing portion 67 by another metal joint 71. Therefore, the solar cells 60 and 61 are electrically connected to each other. Such connection is typically a solar cell connection. When the solar cells are connected to each other, a considerable force is generated that will damage the thin cells. Such a force is transmitted to the solar cells 60 and 61 mainly through the metal joints 70 and 71. Since the reinforcing portions 64, 65, 66, 67 are provided under the joint location of the joints 70, 71, the tin solar cells 60, 61 provide good resistance to the generated force.

  FIG. 7 shows a cross-sectional view of a film 16 and a substrate 8 formed according to a further embodiment of the method. The substrate 8 has a plurality of groove portions 90 parallel to each other on the surface of the substrate 8. These grooves are so narrow that liquid silicon does not crystallize in these grooves, ie, does not form “bridging”. The substrate also has a plurality of recesses 92 that are filled with silicon. These recesses 92 have bottom surfaces that extend substantially parallel to the top surface 94 of the crystallized foil 16. FIG. 8 shows a perspective view of the foil formed in FIG. From FIG. 8, it can be seen that the foil 16 is provided with a zigzag surface from which a plurality of elevations 95 protrude. A metal layer can be formed on the protruding portions 95 by a known printing method such as roller printing. This forms a metal contact that can function to connect the solar cells in a relatively simple manner.

FIG. 9 shows a cross-sectional view of the band-shaped substrate 8 having a plurality of cavities 93 having dimensions and inclination angles that do not fill the silicon melt . This band locally forms a plurality of holes in the silicon panel. The term “hole” refers to a passage. These holes may be round or any shape, for example, a rectangle. These holes can be used in the next processing step where the silicon contacts are connected to the front side and the back side of the foil 16, respectively. Here, the special formation of these holes, for example with a laser, is no longer necessary. These holes preferably have a width of 1 mm to 2 mm. The length, if specified, is determined by the application example. The holes described above can also be formed by providing a high protrusion on the surface of the substrate 8 to penetrate the foil 16. FIG. 10 shows a top view of the embodiment of FIG. It can be seen that nine holes are formed in each silicon panel. FIG. 10 shows cavities 93 arranged in a matrix. Other arrangements and numbers are possible depending on the application of the silicon panel.

FIG. 11 shows another embodiment of the present invention in which the crucible 72 contains a silicon melt 74. A substrate 78 is in contact with the surface of the silicon melt 74 (see FIG. 9). The substrate 78 is connected to a bar 80 that is moved by the driving means 82 so that the substrate 78 slides slowly along the surface of the silicon melt 74. In the example shown in FIG. 11, the driving means 82 is guided by the conveyor path 83. The substrate 78 has a temperature lower than the crystallization temperature of silicon . For this reason, a thin layer of crystallized silicon is formed on the surface of the substrate 78. Since the substrate is also away from the surface, a foil of a predetermined thickness is formed. FIG. 12 shows an example of a bottom view of the substrate 78 of FIG. The substrate 78 has a plurality of groove portions 84, and these groove portions have a width and an inclination angle such that the liquid silicon 74 does not fill the groove portions 84. Alternatively, bridging can be formed to cover these grooves, as already described with reference to FIG. In this embodiment, it is also possible to form a protruding portion on the foil instead of the recess of the foil.

  The formed foil shrinks as it cools. By contracting in this way, the foil is reliably removed from the substrate 78.

It should be noted that the pattern of the foil 16 is actually a mirror image of the pattern formed on the substrate 8 and the method according to the invention in which the panel has only holes and no reinforcements. It should also be noted that can be formed by:

Read the above modification, it is readily subtracted from the state of the art is, Ru understood. Also, the substrate 8 side of the silicon melt 4 is moved, it is possible to foil is flowed upwardly. Such variations are considered to be within the scope of the application as set forth in the appended claims.

Fig. 2 shows a schematic side view of an apparatus according to an embodiment of the invention. FIG. 3 shows a top view of a band-shaped substrate according to one embodiment. 3 shows a cross-sectional view of the substrate of FIG. Figure 2 shows a cross-sectional view of the substrate and the formed foil. FIG. 6 shows a cross-sectional view of a substrate according to another embodiment and a panel formed on the substrate. Fig. 2 shows two solar cells manufactured by a method according to another embodiment and connected to each other. FIG. 4 shows a cross-sectional view of a panel and a substrate formed in accordance with a further embodiment of the method. FIG. 8 shows a perspective view of the foil formed in FIG. 7. FIG. 2 shows a cross-sectional view of a panel and a substrate formed in accordance with one embodiment of the present invention. FIG. 10 shows a top view of the substrate of FIG. 9. Fig. 4 shows a schematic side view of an apparatus according to another embodiment. FIG. 12 shows a bottom view of the substrate of FIG. 11.

Claims (15)

A method for manufacturing a plurality of silicon panels, comprising:
Preparing a container (2, 72) filled with a silicon melt (4, 74) in a dischargeable manner and one or more first grooves (17) extending across the entire width of the silicon panel to be manufactured; ) and has on one side a discharge, the one surface of the substrate (8,78) band-shaped having a lower temperature than the silicon melt as the silicon melt is crystallized, from the container (2,72) Contacting the silicon melt (4, 74) as
Moving the substrate (8, 78) relative to the silicon melt (4, 74) such that a silicon foil (16) is formed on the one surface of the substrate (8, 78);
Separating the silicon foil from the substrate, wherein the silicon foil (16) is divided into silicon panels, respectively, where the first groove (17) is formed,
The band-shaped substrate (8, 78) has at least one second groove (52, 54, 92) on the one surface having a dimension that is substantially filled with the silicon melt , At this location, a thick reinforcement portion of the silicon foil is formed, and thus a thick reinforcement portion is formed in the silicon panel within the at least one second groove (52, 54, 92) and the remaining of the silicon panel A method wherein the portion remains thin and the thick reinforcing portion reinforces the silicon panel as a whole. The method of claim 1, wherein the silicon panel has an average thickness of 100 to 350 µm over the entire surface excluding the reinforcing portion.   The method of claim 1 or 2, wherein the at least one second groove has a depth of 50 to 500 m.   4. The method according to claim 1, wherein the at least one second groove has a width of 2 to 5 mm. The method according to claim 1, wherein the at least one second groove has a bottom surface extending substantially parallel to an upper surface of the silicon panel. The bands-like substrate (8), so that this same pattern is formed on the surface of the silicon panel (16), wherein formed on one surface a recessed well projecting portion of the substrate (8) (22, 23 , 24, 25). A method as claimed in any one of the preceding claims. The method according to claim 6, wherein the band-shaped substrate has a plurality of the recesses having a depth and a width so as to be filled with the silicon melt . 7. The method of claim 6, wherein the band-shaped substrate has a plurality of the recesses having a depth and width such that a bridge is formed by crystallized silicon . The band-shaped substrate has a plurality of the recesses, and each of the recesses has a plurality of cavities (93), and the cavities (93) are formed on the substrate (8). The method of claim 6 having dimensions such that holes are respectively formed in the silicon panel.   The method of claim 6, wherein the protruding portion comprises a plurality of strips. The band-shaped substrate (8) has at least one recess (93) on the one side, and the recess has a dimension such that crystallization of the liquid silicon does not occur in the at least one recess. The method of claim 1, wherein as a result, holes are formed locally in the silicon panel. The band-shaped substrate (78) is brought into contact with the silicon melt (74) 1 on the surface of the silicon melt (74) filled in the container and guided away from the silicon melt. Item 2. The method according to Item 1 . Claims 1 to 12 or 1 silicon panels prepared by the process of. An apparatus for manufacturing a plurality of silicon panels,
A container (2, 72) for containing a silicon melt in a dischargeable manner ;
Has one or more first groove extending over the entire width of the silicon panels to be produced (17), maintained at least during operation at a lower temperature than the silicon melt as the silicon melt is crystallized is either in contact with the silicon melt in the container, so as to be in contact with the silicon melt from the container, a band-shaped substrate is moved relative to said container (8,78),
The substrate is placed into contact with the silicon melt on one surface of (8), and a silicon foil to move the substrate (8) to the silicon melt so as to form on one surface of the substrate (8) In which the silicon foil (16) is divided into silicon panels where the first groove (17) is formed, respectively,
The band-shaped substrate (8) has at least one second groove (52, 54, 92) on the one side with a dimension such that it is substantially filled with the silicon melt , thus A thick reinforcement portion is formed in the silicon panel within the at least one second groove (52, 54; 92), and the remaining portion of the silicon panel remains thin, and the thick reinforcement The device is characterized in that the part reinforces the entire silicon panel. The band-shaped substrate (8) has at least one recess (93) on the one side, and the recess has a dimension such that crystallization of the silicon melt does not occur in the at least one recess. and, this as a result, holes, according to claim 14, characterized in that it is formed locally in the silicon panel.

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